To use an alternate compressor class, provide a class with a compile class
method accepting arg text and kwargs mimetype, cwd, uri_cwd,
and debug. For example, to use
libsass-python for SASS files
instead of the built-in SassCompressor, create your custom compressor class:

To only customize the path of a compressor which forks a subprocess for the
compile step (LessCompressor, CoffeeScriptCompressor, and SassCompressor), just
extend the compressor class and overwrite the binary class attribute: